1. Field of the Invention
The present invention relates to flow monitoring devices. More particularly, the present invention relates to probes for monitoring the flow of groundwater.
2. Discussion of Background
Many devices that measure the flow of liquids are known to exist. Moreover, existing devices are known that measure specifically the magnitude and direction of groundwater flow beneath the earth's surface. Similarly, devices that measure fluid flow in other media are also known.
For example, Walsh, in U.S. Pat. No. 4,570,492, describes a flowmeter that measures liquid flow by electrochemical emission and detection. The flowmeter is specifically useful as a speed indicator for nautical vessels, and the like. The device has an upstream source that periodically discharges a known chemical into the liquid flow. A downstream probe detects the arrival of the chemical and communicates the information to an electronic circuit for determining the liquid flow rate.
For groundwater flow, Foster et al (U.S. Pat. No. 4,963,019) disclose a device that uses light refraction for detecting flow. Light from a light source passes through groundwater to a photodigitizer. Light refracted by suspended particulate is correlated with the direction of flow of the groundwater.
Kerfoot et al, in U.S. Pat. No. 4,391,137, disclose a groundwater flow detector using thermal differentials as a basis for detecting flow. The device operates by transferring a known quantity of heat across a porous, heat conductive medium along with the flowing groundwater. A series of temperature sensors near the medium detects the temperature differentials, which are then mapped and used in determining the groundwater flow rate.
Dunn et al, in U.S. Pat. No. 4,547,080, disclose a groundwater flow sensor that uses a thermal perturbation technique to determine the groundwater flow velocity in the immediate vicinity of the probe. The device consists of a long thin cylinder with a heater and an array of temperature sensors on its surface. The heater warms the ground and the groundwater surrounding the device. In the presence of a flow field past the probe the temperature distribution on the surface of the device is perturbed as heat emanating from the probe is advected around the device. Relatively cool temperatures occur on the upstream side of the cylinder and relatively warm temperatures occur on the downstream side. In this manner, Dunn et al employ the diffusion of heat from the probe and measure the temperature distribution on the surface of the probe.
It is believed that no flow monitoring device diffuses an electrolyte from the surface of the device and uses the measurement of the distribution of electrical conductivity on the surface of the device as a means for detecting the magnitude and direction of such flow.